Current Navy methods for reacquisition, identification and neutralization (RIN) of mines in very shallow water (i.e., 10-40 feet) and surf zone (i.e., 0-10 feet) utilize divers and/or marine mammals (e.g., dolphins and sea lions) to relocate contacts found by mine search sonars and to deploy countercharges to destroy the mines. These approaches risk personnel who must enter the minefields and endanger themselves by being visible on the surface from enemy shores, and by having to work around mines while in moving currents and waves.
Recently, unmanned vehicles have been used to search for and neutralize mines. Unmanned underwater vehicles (UUVs) that swim in the water column are currently in the fleet for performing search, classify and mapping (SCM) missions. These swimming vehicles are ideal for carrying side-scan sonar to perform wide area reconnaissance of minefields. They can efficiently scan large areas and map mine-like sonar contacts. Under ideal conditions, UUVs can identify sonar contacts using cameras or specialized imaging sonars. However, it is difficult for UUVs to place countercharges on the mines or to identify them under poor optical or acoustic conditions. In addition, UUVs generally rely on acoustic navigation aids which must be pre-positioned within the minefield before the vehicles can function. The UUVs must be delivered near to or into the minefields by personnel in boats thereby endangering the delivery personnel.
Bottom-crawling robots (i.e., “crawlers”) provide a stable base for identifying and prosecuting mines that were contacted by a UUV and are thus ideal for performing the RIN mission. A crawling robot can approach an object and apply sensors (e.g., image the object) at contact range. The natural stability of the crawler and the fact that it moves along the bottom offers the opportunity to exploit new target features for identification of mine-like contacts. The crawler can neutralize mines easily by dropping a countercharge or by serving as a sacrificial, mobile countercharge.
However, crawlers cannot transit long distances. Further, they can easily become stuck while transiting over rough bottoms. Still further, because of their limited energy, personal in boats must deliver the crawlers into or close to the minefields. For these reasons, crawlers have been considered only for limited use for performing mine neutralization missions.
Vehicles that can both swim and crawl have limited payload, speed, and range capabilities. The limitations derive mostly from the physics of buoyancy since it is necessary for the vehicle to release either ballast or buoyancy material to enable it to swim or to be heavy enough to navigate along the bottom and stay in place to neutralize a mine.